interface postgres {
  use rdbms-types.{parameter-value, row-set};

  // General purpose error.
  variant pg-error {
      success,
      connection-failed(string),
      bad-parameter(string),
      query-failed(string),
      value-conversion-failed(string),
      other-error(string)
  }

  // query the database: select
  query: func(address: string, statement: string, params: list<parameter-value>) -> result<row-set, pg-error>;

  // execute command to the database: insert, update, delete
  execute: func(address: string, statement: string, params: list<parameter-value>) -> result<u64, pg-error>;
}